The present disclosure relates generally to auxiliary milling units for milling machines.
Conventional milling machines, such as computer numeric control (CNC) milling machines, includes a main spindle holding a milling tool that is used to perform machining operations, such as milling holes. The main spindle is supported by, and moved by, a movement assembly, such as a carriage, an arm, and the like, to position the milling tool above a workpiece for machining. In some applications, holes are milled in the workpiece using the milling tool. The main spindle is moved in a circular motion by the movement assembly to bore and enlarge the hole to the desired diameter.
However, when making relatively small features such as holes, the movement assembly is unable to move quickly enough to move the main spindle to accurately bore the hole. For example, due to the large mass of the main spindle and movement assembly, small movements, such as the circular motion to bore out the holes, are difficult to control accurately when performed quickly. As such, when performed quickly, the holes may be oblong. Furthermore, the small movements wear the milling machines over time, which are expensive to repair or replace.
One solution to improving the accuracy of machining the holes is to slow down the milling process. However, while improving the accuracy of the machining, slowing down the boring process adds additional machining time and reduces throughput. Another solution to machining the holes in the workpiece is to use separate milling machines or different milling tools to make the different sized holes. However, providing different milling machines is expensive and requires a large amount of floor space in the manufacturing facility. Additionally, the workpiece may need to be moved to the various machines, which adds time and labor to the machining process. Using different milling tools requires changing out the milling tools which creates a significant amount of machine time for the change out. For instance, in one example, three different size holes are made in the workpiece. The milling tool change may be approximately 1 minute for each milling tool adding significant time to machine the workpiece.
A need remains for a milling machine capable of machining a workpiece in a cost effective and reliable manner.